Monitoring and Mapping of Rice Cropping Pattern in Flooding Area in the Vietnamese Mekong Delta Using Sentinel-1A Data: A Case of An Giang Province

Abstract

Cropping intensity is one of the most important decisions made independently by farmers in Vietnam. It is a crucial variable of various economic and process-based models. Rice is grown under irrigated triple- and double-rice cropping systems and a rainfed single-rice cropping system in the Vietnamese Mekong Delta (VMD). These rice cropping systems are adopted according to the geographical location and water infrastructure. However, little work has been done to map triple-cropping of rice using Sentinel-1 along with the effects of water infrastructure on the rice cropping intensity decision. This study is focused on monitoring rice cropping patterns in the An Giang province of the VMD from March 2017 to March 2018. The fieldwork was carried out on the dates close to the Sentinel-1A acquisition. The results of dual-polarized (VV and VH) Sentinel-1A data show a strong correlation with the spatial patterns of various rice growth stages and their association with the water infrastructure. The VH backscatter (σ°) is strongly correlated with the three rice growth stages, especially the reproductive stage when the backscatter is less affected by soil moisture and water in the rice fields. In all three cropping patterns, σ°VV and σ°VH show the highest value in the maturity stage, often appearing 10 to 12 days before the harvesting of the rice. A rice cropping pattern map was generated using the Support Vector Machine (SVM) classification of Sentinel-1A data. The overall accuracy of the classification was 80.7% with a 0.78 Kappa coefficient. Therefore, Sentinel-1A can be used to understand rice phenological changes as well as rice cropping systems using radar backscattering.

Groundwater Quality Assessment Using Fuzzy-AHP in An Giang Province of Vietnam

“…Although As concentration in An Giang was under the permissible limits of the National technical regulation on groundwater quality (0.05 mg/L) since 2014, it still exceeds the WHO permissible limit of 0.01 mg/L [50]. There is insufficient evidence to conclude whether agricultural activity affects aquifer.…”

“…An Giang province is part of the agricultural intensification region of the VMD, where the water regime is mainly under human control through sluice gates, canals, and dike systems [47][48][49]. The land use/land cover (LULC) map of An Giang shows the percentage of various LULC classes in 2018 with a triple, double, and single rice crop, and other classes that cover 46.6%, 24.7%, 7.3%, and 21.4%, respectively [50]. The highly irrigated triple and double rice crops occur inside the dike system using surface water, which has negative impacts on surface and groundwater quality especially in the full-dike system [29,46].…”

Effects of Multi-Dike Protection Systems on Surface Water Quality in the Vietnamese Mekong Delta

“…The high nutrients in the dry season can be attributed to the wastewater that is discharged directly into the canal system from fishponds on secondary canals, as well as from households, markets, and tourists on primary canals. Moreover, people often live along the riverbanks of primary canals and rely on them for their livelihoods, while farmers often construct minor canals (or ditches) for irrigation and drainage from their rice fields [39]. Thus, the fresh water resources inside the dike system were not very suitable for aquatic life.…”

Remote Sensing for the Quantification of Land Surface Dynamics in Large River Delta Regions—A Review

“…This first continental-scale, multi-decadal assessment of annual mangrove distribution showed that mangrove forest extent in Australia peaked in 2010 and has since declined by about 240 km 2 [139]. Several recent studies have used Sentinel-1 SAR time series data to map the distribution of rice paddies and aquaculture ponds in river deltas, taking advantage of the unique seasonal inundation dynamics and microwave backscattering characteristics of these features [171,172,[188][189][190]. Advances in SAR-based mapping of aquaculture ponds are already covered in the previous chapter, and therefore, are not repeated here.…”